DESCRIPTION
The invention relates to a semiconductor device comprising a semiconductor body which includes at least an active element with a pn junction, the surface of the semiconductor body being provided with an electrically insulating layer on which a conductor track is situated, which is made of a metal having a lower resistivity than aluminium, which electrically insulating layer is provided with an aperture which contains a metal which electrically connects the conductor track to the active element or to an aluminium conductor track, the walls and the bottom of said aperture being provided with an electroconductive layer forming a diffusion barrier for the metal. The invention also relates to a simple method of manufacturing such a device.
Such a device is, for example, an IC (=Integrated Circuit). The active elements used in successive generations of such an IC are becoming smaller and smaller. In this connection, also the conductor tracks, which are responsible for the electric connection of the elements, are becoming ever smaller. If very small conductor tracks are made of aluminium, the resistance of the conductor tracks becomes too high. As a result, it is necessary to manufacture the conductor tracks from a metal having a better resistivity, such as copper, silver or gold.
Such a device is known from United States patent specification EP 0.751.566, published on Jan. 2, 1997. This patent document shows an IC comprising a copper conductor track on an electrically insulating layer, which conductor track is connected to an underlying aluminium conductor track via an aperture in the insulating layer which is also filled with copper. The side walls and the bottom of the aperture are provided with an electroconductive layer, which comprises tantalum nitride and forms a diffusion barrier for the copper. Also the copper conductor track is surrounded by such a layer.
A disadvantage of the known device is that the electroconductive layer, which serves as a diffusion barrier for copper, adversely affects the resistance of a conductor track or connection. The material of such a barrier has a higher resistivity than, for example, copper, and the barrier must be sufficiently thick if it is to serve as a diffusion barrier. In addition, undesirable interaction may occur between the material of the barrier and, for example, copper. Besides, the impact of these drawbacks becomes relatively large as the conductor tracks become smaller. Also the manufacture of such a device is relatively complex.